Efficacy and safety of glecaprevir/pibrentasvir in HCV-infected Japanese patients with prior DAA experience, severe renal impairment, or genotype 3 infection

Background Once-daily, orally administered, co-formulated glecaprevir (NS3/4A protease inhibitor) and pibrentasvir (NS5A inhibitor) (G/P) demonstrated pangenotypic activity and high sustained virologic response (SVR) rates in studies outside Japan. Here we report safety and efficacy in a subset of Japanese patients with chronic HCV infection who received G/P 300/120 mg in a phase 3, open-label, multicenter study (CERTAIN-1). Methods This analysis focuses on three difficult-to-treat subgroups: HCV GT1/2-infected patients who failed to achieve SVR after treatment with a direct acting antiviral (DAA)-containing regimen; GT1/2-infected patients with severe renal impairment (estimated glomerular filtration rate < 30 mL/min/1.73 m2); and GT3-infected patients. Patients in the renal impairment and GT3 cohorts were treatment-naive or interferon treatment-experienced. Noncirrhotic GT1/2-infected, DAA-naïve patients in the renal impairment cohort received G/P for 8 weeks; all other patients were treated for 12 weeks. Primary outcome was SVR (HCV RNA < 15 IU/mL) 12 weeks post-treatment (SVR12). Results The study enrolled 33 GT1/2-infected patients who failed previous DAA treatment (four with cirrhosis); 12 GT1/2-infected patients with severe renal impairment (two with cirrhosis); and 12 GT3-infected patients (two with cirrhosis). SVR12 was achieved by 31/33 (93.9%), 12/12 (100%), and 10/12 (83.3%) patients, respectively. One serious adverse event (fluid overload, not related to G/P) occurred in a patient on chronic intermittent hemodialysis. Conclusions G/P achieved high SVR12 rates and was well tolerated in three difficult-to-treat patient subgroups with limited treatment options in Japan (DAA-experienced patients, patients with severe renal impairment, and GT3-infected patients). These results support the potential suitability of this regimen for these special populations in Japan. Electronic supplementary material The online version of this article (doi:10.1007/s00535-017-1396-0) contains supplementary material, which is available to authorized users.

The Japan Society of Hepatology (JSH) guidelines for the management of hepatitis C virus infection recommend ledipasvir/sofosbuvir for HCV GT1-infected and sofosbuvir ? RBV for GT2-infected patients without severe renal impairment who previously failed to achieve SVR with a prior protease inhibitor (PI) ? pegylated interferon (pegIFN) ? RBV regimen [11]. For GT1-infected patients who failed previous PI ? NS5A-inhibitor therapy, retreatment with simeprevir ? pegIFN ? RBV, or ledipasvir/sofosbuvir are recommended options dependent on patient and viral characteristics. Since there is insufficient evidence on the impact of DAA-resistance in ledipasvir/sofosbuvir failures on future treatment, the JSH guideline also suggests considering anticipating new drug development as an option [11].
There are currently no approved treatment options for GT2-6-infected patients with severe renal impairment in Japan. IFN-free DAA combination regimens of sofosbuvir ? RBV and ombitasvir/paritaprevir/ritonavir ? RBV are recommended for some HCV GT2-infected patients. However, sofosbuvir is contraindicated for use in patients with severe renal dysfunction regardless of genotype. Additionally, RBV, is contraindicated in patients with moderate or severe renal impairment and should be avoided in patients with severe cardiac conditions, leaving GT2-infected patients with these comorbidities without an IFN-free treatment option.
For GT3 infected patients, treatment options include pegIFN ? RBV, which produces low SVR rates (68%) and has poor tolerability, particularly in the elderly and patients with comorbidities such as psychiatric illness, autoimmune disorders, and cytopenias [12][13][14], and the recently approved DAA-based regimen sofosbuvir ? RBV for 24 weeks, which produces an SVR rate of 85% [15]. Both of these regimens contain RBV and are thus subject to the contraindications and associated with adverse events typical of RBV (e.g., hemolytic anemia and pruritus).
Hence, there is an unmet need for a single potent, once a day, well-tolerated, RBV-and IFN-free pangenotypic regimen with high efficacy in the majority of GT1 or GT2 HCV-infected, DAA-naive Japanese patients, including those with stages 4 or 5 CKD, as well as other special populations with limited treatment options, that could help simplify and improve the current standard of care in HCVinfected Japanese patients.
Glecaprevir (GLE, formerly ABT-493, identified by AbbVie and Enanta), an NS3/4A protease inhibitor coformulated with pibrentasvir (PIB, formerly ABT-530), an NS5A inhibitor, is currently being evaluated as a pangenotypic regimen (G/P) for patients with chronic HCV infection including ''difficult-to-treat'' subgroups such as patients with compensated cirrhosis, chronic renal failure, or those who failed to respond to previous DAA-based therapy. Preclinical studies have demonstrated that this combination regimen has a high barrier to resistance and potency against common NS3 and NS5A polymorphisms [16]. High efficacy of G/P in various patient populations over short treatment durations compared to currently recommended treatments has been demonstrated outside Japan, including in patients who have been previously considered difficult-to-treat. Here we describe the safety and efficacy of G/P in GT1 or GT2 HCV-infected patients who failed to achieve SVR with prior DAA-treatment or those with severe renal impairment including those with compensated cirrhosis, and in GT3 HCV-infected patients.

Study design
CERTAIN-1 is a phase 3, open-label, multicenter study assessing the safety and efficacy of G/P (300/120 mg) once daily in Japanese patients with HCV infection. Results from substudy 1 where HCV GT1-infected patients without cirrhosis were treated for 8 weeks with G/P or 12 weeks with ombitasvir/paritaprevir/ritonavir, as well as patients in substudy 2 with HCV GT1 and GT2 infection and compensated cirrhosis treated with G/P for 12 weeks have been reported elsewhere [17,18]. Here we report on the remainder of patients in substudy 2 who belong to four special populations: HCV GT1-or GT2-infected patients who failed prior DAA-treatment including patients with compensated cirrhosis, GT1 or GT2 HCV-infected patients with severe renal impairment and compensated cirrhosis, GT3 HCV-infected patients who were treatment-naive or IFN treatment-experienced, all of whom received treatment with G/P for 12 weeks, and patients with GT1 or GT2 HCV infection with severe renal impairment without cirrhosis who received treatment for 8 weeks. In this report we combine the results from patients with severe renal impairment with or without compensated cirrhosis. Figure 1 shows the study design.
All patients provided written, informed consent to participate, and the study was conducted consistent with the ethical guidelines of the Declaration of Helsinki and the International Conference on Harmonisation Good Clinical Practice Guidelines. The study was approved by an institutional review board of each study site prior to the initiation of any screening or study-specific procedures. Supporting Figure 1 shows patient disposition.

Patients
Patients were screened from February 22, 2016 to June 1, 2016 at 62 study sites in Japan. Adults 18 years or older were eligible for enrollment if they had chronic HCV GT1 to GT6 infection documented by positive anti-HCV antibody test and a plasma HCV RNA level C 1,000 IU/mL at the time of screening. Plasma samples for HCV genotype and subtype determination were collected at screening and assessed using the appropriate assay by the central laboratory.
Presence or absence of compensated cirrhosis was determined by liver biopsy, Fibroscan, FibroTest/aspartate aminotransferase to platelet ratio index, or discriminant score test. Additional details are listed in the Supporting Information. The study population comprised patients with and without compensated cirrhosis and HCV GT1 or GT2 infection who failed to achieve SVR with at least 1 approved, commercially available HCV DAA-containing regimen C 2 months prior to screening were enrolled as prior DAAfailures. In addition, HCV GT1 or GT2 infected patients with severe renal impairment (with or without compensated cirrhosis) and an estimated glomerular filtration rate (eGFR) \ 30 mL/min/1.73 m 2 [using the MDRD method modified for Japanese population: eGFR J = 194 9 Serum Creatinine -1.094 9 Age -0.287 9 0.739 (if female)], including patients with end-stage renal disease requiring treatment with chronic intermittent hemodialysis were also enrolled.

Study assessment
Virologic response was assessed by plasma HCV RNA levels at various time points. Samples were collected at the screening visit, Day 1 visit and treatment Weeks 1, 2, 4, 8 (and 12 for patients with 12-week treatment duration) and post-treatment Weeks 2, 4, 8, 12, and 24. Plasma HCV RNA levels were determined for each sample collected by the central laboratory using the Roche COBAS Ò Ampli-Prep/COBAS Ò TaqMan HCV Quantitative Test, v2.0. The lower limit of detection (LLOD) and lower limit of quantification (LLOQ) for this assay (regardless of genotype) were both 15 IU/mL. The efficacy endpoints for the three cohorts reported in this analysis are the percentage of patients achieving SVR 12 , the percentage of patients with virologic failure during treatment and relapse post treatment.
Next-generation sequencing was performed on samples collected from all patients at baseline, and presence of HCV baseline polymorphisms in NS3 and NS5A was evaluated using a 15% detection threshold. For patients who experienced virologic failure, treatment-emergent substitutions in NS3 and NS5A relative to the patient's baseline HCV sequence were analyzed. Blood samples for pharmacokinetic (PK) assessment of the study drugs were collected from patients during each study visit. Patients consenting to intensive pharmacokinetic sampling had samples drawn at the Study Day 1 (at 2, 4, and 6 h postdose) and at Week 4 visit at hour 0 (before study drug administration) and 2 and 4 h post-dose. Plasma concentrations for GLE and PIB were summarized as steady-state trough levels (C trough ) based on binning of PK samples fall in the interval of 22-26 h after dosing. Plasma concentrations were determined using a validated assay at AbbVie.
Treatment-emergent adverse events (TEAEs) and laboratory tests were assessed and recorded throughout the treatment period until 30 days following discontinuation of study treatment. After the 30 day post treatment visit until the post-treatment Week 24 visit only spontaneously reported serious AEs (SAEs) were collected. All AEs were graded according to Common Terminology Criteria for Adverse Events (CTCAE), version 4.0.

Statistical analysis
Analysis of these special populations was conducted after all enrolled patients completed the post-treatment Week 12 visit. Efficacy, safety, and demographic analyses were performed on all patients in the intent-to-treat (ITT) population, defined as all patients who received at least one dose of study drug. The number and percentage of patients achieving SVR 12 , with on-treatment virologic failure and post-treatment relapse and a 2-sided 95% confidence interval (CI) using the Wilson's score method were computed. Descriptive statistics, such as the number of observations, mean, and standard deviation were provided for continuous variables.

Baseline patient demographics and characteristics
A total of 57 patients were included in this analysis; 33 in the failed prior DAA treatment cohort, 12 in the severe renal impairment cohort, and 12 in HCV GT3-infected cohort. Of those, 61, 50, and 50% were female in the three cohorts, respectively. The mean (SD) HCV RNA at baseline was 6.0 (0.5), 5.8 (1.2), and 6.2 (0.7) log 10 IU/mL, respectively. The median age in the three cohorts was 67, 69, and 57 years, respectively. Compensated cirrhosis was present in 12% of DAA-experienced patients, 17% of those with severe renal impairment, and 17% in those with GT3 infection. Among DAA-experienced patients, most had also failed a prior DAA-free, IFN-containing regimen, and 91% had failed prior daclatasvir ? asunaprevir treatment. Detailed patient demographic and baseline characteristics are outlined in Table 2.
Efficacy outcomes SVR 12 was achieved by 31/33 (93.9%; 95% CI 80.4-98.3%) patients who failed to achieve SVR with at During the study, two noncirrhotic GT3 infected patients failed to achieve SVR 12 . One subject was treatment-naive who relapsed at post-treatment Week 12. The plasma concentrations of this subject were comparable to other GT3 subjects who achieved SVR 12 (pharmacokinetic data not shown). The second GT3-infected subject who failed to achieve SVR 12 had received prior interferon-based treatment and relapsed at post-treatment Week 2. The plasma concentrations of this subject were substantially low for both GLE (ranging from 7.6 to 10.6 ng/mL) and PIB (ranging from 8.8 to 13.2 ng/mL) during weekly treatment visits). Figure 2 shows the SVR 12 rates and 95% CI for the ITT population of all groups.

Analysis of resistance
Prevalence of baseline polymorphisms in HCV from 10 of the 12 patients with renal impairment is shown in Supporting Table 2 (data not available for 2 patients). Baseline polymorphisms were not detected in NS3, while baseline NS5A polymorphisms were detected in 7/10 patients.
In this study, 30/32 GT1b-infected patients had previously received asunaprevir ? daclatasvir. Two of these 30 (6.7%) patients had P32 deletion in NS5A at baseline; both of these patients experienced virologic failure. P32 deletion in NS5A confers[ 1000-fold resistance to PIB. Treatmentemergent substitutions A156D/V in NS3 were detected in one of the two patients who had virologic failure (D168V was also present at baseline and post-baseline in this patient). In NS5A, P32 deletion and L31F/P32 deletion   were each present in one of the virologic failure patients at both baseline and post-baseline (Supporting Table 3). The single GT2-infected DAA-experienced patient achieved SVR 12 . Two GT3-infected patients experienced virologic failure, one infected with GT3b and one infected with GT3k (Supporting Table 3). Twelve GT3-infected patients were enrolled in this study and included diverse subtypes (7 GT3a, 4 GT3b, 1 GT3k). One of the two patients with GT3 infection who failed to achieve SVR 12 had unusually low plasma concentrations of G/P. Therefore, the impact of baseline polymorphisms on treatment outcome in GT3-infected patients could not be meaningfully assessed.

Pharmacokinetic results
Following administration of G/P, GLE and PIB plasma concentrations attained steady state by Week 1 visit and remained constant throughout the treatment period (Week 1-Week 8 for non-cirrhotic patients with severe renal impairment with or without dialysis and Week 1-Week 12 for DAA-experienced or cirrhotic patients with severe renal impairment or patients with GT3 infection). The binned geometric mean trough plasma concentrations of GLE and PIB in these subjects are shown in Supporting Table 4. GLE and PIB plasma concentrations were comparable between the 8-and 12-week treatment durations irrespective of prior treatment history or the presence of severe renal impairment. No apparent drug accumulation was observed. GLE plasma concentrations were higher in patients with compensated cirrhosis compared to patients without cirrhosis across all study populations while PIB plasma concentrations were comparable between patients with and without cirrhosis.

Safety outcomes
TEAEs were experienced by 64%, 83%, and 67% of patients in the DAA-experienced, severe renal impairment and GT3 cohorts, respectively, with 33%, 42%, and 33% assessed as study drug related by investigator. No patient discontinued study drug due to adverse events. One patient with severe renal impairment on hemodialysis experienced an SAE (fluid overload) that was assessed by the investigator as not being study-drug related. TEAEs that occurred at a frequency C 10% in any single cohort included nasopharyngitis, headache, pruritus, abdominal distension, rash, blood creatinine increase, and arthralgia (Table 4).
Laboratory abnormalities were rare across all treatment groups. No grade C 3 elevations (worsening from baseline) occurred in hemoglobin, alanine aminotransferase (ALT), aspartate aminotransferase (AST), or total bilirubin levels ( Table 5).

Discussion
In this analysis, Japanese patients with limited treatment options: prior DAA-treatment experience, severe renal impairment, or GT3 HCV-infection, achieved SVR 12 rates of 93.9%, 100%, and 83.3%, respectively, following 8 or 12 weeks of G/P treatment. Four patients experienced virologic failure, including two DAA-experienced and two GT3-infected patients. The two DAA-experienced GT1binfected patients were previously treated with asunaprevir ? daclatasvir and both had P32 deletion in NS5A at baseline. P32 deletion in NS5A has been observed as an uncommon treatment-emergent substitution in patients who have been treated with a daclatasvir-containing regimen [19,20]. In this study P32 deletion was detected in two of 30 patients who were previously experienced to this regimen. Among DAA-experienced patients, the primary baseline polymorphisms in NS3 and/or NS5A, including those at amino acid position 168 in NS3 or at positions 31 or 93 in NS5A, had no impact on SVR 12 . Of the two GT3infected patients who had virologic failure, one was treatment-naive and one was pegIFN/RBV-experienced. Plasma concentrations of GLE and PIB were very low throughout treatment in the latter patient without a plausible medical explanation.
The G/P regimen was well-tolerated with no drug-related SAEs reported, no discontinuations of study drug due to AE, and no grade C 3 laboratory abnormalities in hemoglobin, ALT, AST or bilirubin levels observed. Three patients experienced Grade 2 total bilirubin elevations, though none had concurrent ALT elevation or other laboratory abnormality indicative of liver disease progression, and all cases recovered without intervention. Additionally, there were no cases of hepatic decompensation, and no events consistent with drug-induced liver injury were reported. The low rates of laboratory abnormalities observed in this study were also observed in Japanese patients with GT 1 or 2 infection without cirrhosis and with compensated cirrhosis enrolled in the CERTAIN studies and treated with G/P (reported elsewhere [17,18]). Similar overall safety results were observed across all phase 2 and phase 3 studies conducted outside Japan. The favorable safety profile across all cohorts may enable G/P to be used in broad patient populations, including HCV GT2-6-infected patients with severe renal impairment (CKD 4 and 5; eGFR \ 30 mL/min/1.73 m 2 ), who currently have no treatment options.
Results from this study are encouraging in light of the currently available treatment options in Japan for the patient populations included in this analysis. According to JSH guidelines, retreatment options are limited for GT1 patients who fail to achieve an SVR with a PI ? NS5A inhibitor; moreover, resistance testing is required to select an appropriate regimen. There is no treatment regimen available for GT2-6-infected patients with severe renal impairment, and the only treatment regimen available for GT3-6 patients is 24 weeks in duration and requires RBV [11]. Both DAA-containing regimens currently approved for treatment of Japanese patients with HCV GT2 infection require co-administration of RBV which is contraindicated in patients with moderate or severe renal impairment. Studies of G/P conducted outside Japan have shown high  SVR 12 rates for patients who failed prior DAA therapy [21], patients with severe renal impairment (including those receiving hemodialysis) [22], and treatment-naive patients with GT3 [23]. The findings of this study in Japanese patients are consistent with studies conducted in non-Japanese patients.
In summary, high SVR 12 rates were achieved with G/P in patients with limited treatment options in Japan, including those with prior DAA experience (93.9%), those with severe renal impairment (100%), and those with GT3 HCV infection (83.3%), and treatment was well-tolerated. These results demonstrate the high efficacy and favorable safety and tolerability of G/P for Japanese patients, including those who currently have limited treatment options.